Name Resolution Facts Flashcards
Fully qualified domain name
(FDQN)
Includes the hostname and the names of all domains between the host and the root.
Root
This is the highest domain in the DNS hierarchy and is separated from the Top Level Domain by a dot.
Example: testout.com
Top-level domain
(TLD)
Highest level of the domain names. The names are delegated to specific organizations such as .com, .edu, and .gov.
Second-level domain
(SLD)
Second-level domains are located directly below the top-level domain and are generally referred to as the organization that registered that domain name.
Hostname
(domain name)
The first part of the FDQN. WWW, for example, is the most common web server domain name.
Forward lookup
A forward lookup uses the hostname or a FDQN to find the IP address.
Reverse lookup
A reverse lookup uses the IP address to find the hostname or FDQN.
Authoritative server
An authoritative server is a DNS server with a complete copy of all records for a particular zone.
Referral
Referral is the process by which the DNS servers use one another to resolve requests from the specific clients. Because each DNS server is responsible for a small piece of the DNS namespace, the servers contact one another when they cannot resolve queries from their own clients. For example, a root DNS server refers to the DNS servers to .com, .edu, or .gov DNS servers.
Recursion
Recursion is the process in which a DNS server or host root name server and subsequent servers perform name resolution. Most client computers do not perform recursion. Instead, they submit a DNS request to the DNS server and wait for a complete response. Many DNS servers perform recursion.
Iterative
Iterative is the process by which a DNS server requests information from the request to another DNS server.
Delegation
Delegation is the process by which a DNS server hands responsibility for the request to another DNS server.
DNS forwarders
A forwarder is a DNS server on an internal network configured to forward DNS queries for the external DNS names to DNS servers on other domains or outside the network. External DNS names could exist in other domains, other networks, or on the internet.
Root hints
If a DNS forward is not configured, the internal network DNS server will use root hints of external DNS names to a root-level DNS server on the internet. By default, DNS servers are configured with a root hints list that contains the addresses of all the root-level DNS servers on the internet.
If your organization’s security requires that your internal network not be connected to the internet, you should configure an internal DNS server as authoritative for root(.), and then configure the root hints list on other internal DNS servers with an entry for that server. Also, remove the default root hints list from those DNS servers.
Client
The process for DNS name resolution on the client is as follows:
Entries in the Hosts file are preloaded into the cache.
The host file is located in the c:\windows\system32\drives\etc folder.
All changes to the hosts file are made manually. To change the hosts file, open the file in notepad with elevate privilege and make the changes.
You should use the hosts file only when you want to direct the DNS to a host different than the host listed on the DNS server.
You may want use the host file if you cannot remove an entry from the DNS.
The client examines its local DNS cache for the IP address. The cache holds hostnames that the client has resolved in the past. Entries stay in memory for a short time so that the hostnames in the cache are periodically resolved.
If the IP address is not in the cache, the client sends the request to the DNS server.
